Abstract
The research analyzes the institute of criminal protection of investigative secrecy, comparing the norms on the subject of the European Union, the jurisprudence of the ECHR and the legislation, doctrine and jurisprudence of some European national legal systems, in particular France, Spain and UK. Starting from the institute in question, the relationships and influences between individual national criminal laws and the European legal system were analyzed. The institute in the EU standardization and in the ECHR jurisprudence has had a complex and contradictory evolution, made up of reforms and jurisprudential changes. In the examination of single legal systems, it emerged that the problems posed by this subject today seem far from being resolved. The deepening of the experience of selected single national laws has allowed us to highlight how each country has elaborated original solutions to the complex problems posed to the jurist by the criminal protection of the secret investigation.